1. Field of the Invention
The present invention relates to fuel cartridges for fuel cells, and fuel cell systems that use fuel cartridges.
2. Description of the Related Art
Conventional fuel cell units include a fuel cell and a reserve tank, and fuel cartridges are used for supplying fuel to the fuel cell that produces electrical energy from liquid fuel. One type of known fuel cartridge is designed to replenish the reserve tank in the fuel cell unit with fuel. The fuel cartridge usually contains the liquid fuel directly in a case that is deformable when pressed by a human hand, with a valve section at one end to discharge the fuel. When replenishing the reserve tank in the fuel cell unit with fuel, the fuel cartridge is set upright so that its valve section is positioned lower than the fuel liquid surface, and is pressed by a human hand to pour out the liquid fuel. After that, the pressure on the case is released so as to cause a backflow of outside air from the fuel cell unit side while the case recovers its initial shape.
Another type of fuel cartridge, which is used as attached in the fuel cell unit, includes an inner bag or its counterpart inside a high-rigidity outer case of the cartridge, the liquid fuel being contained inside the inner bag or its counterpart, so that the liquid fuel can be taken out irrespective of the attachment direction of the fuel cartridge (see, for example, Japanese Patent Laid-Open Publication No. 2003-308871).
The problem with fuel cartridges that directly contain the liquid fuel in the case is that part of the fuel, i.e., the volume below the liquid surface that is positioned lower than the valve, cannot be taken out. Thus, with the fuel cell unit that uses a fuel cartridge directly containing liquid fuel, there are limitations on the direction of attachment of the fuel cartridge so that the fuel is poured out almost entirely into the reserve tank by pressing the case with a human hand. The fuel replenishment efficiency and cartridge usability are therefore poor and, very often, the fuel inside the case cannot be used completely.
In a design in which the fuel cartridge is set inside the fuel cell unit and fuel is sucked out using a pump provided in the fuel cell unit, the same problem applies, i.e., part of the fuel, the volume below the valve cannot be taken out.
With the fuel cartridge that contains liquid fuel in the inner bag inside the rigid outer case, it is not possible to inject fuel into the reserve tank of the fuel cell unit with a human hand. Furthermore, the usability is poor because this fuel cartridge cannot be conveniently used in both applications where the cartridge is set inside the fuel cell unit and where the fuel is injected from the cartridge into the reserve tank of the fuel cell unit by a human hand.